This invention relates to a protective lens array in which particle induced gas breakdown absorbs laser power.
1. Background Art
U.S. Pat. No. 6,028,732 discloses a lens for protecting high gain optical systems (eyes or equipment) from laser radiation pulses of about one microsecond duration and less. One embodiment comprises a normal binocular system which focuses the radiation at a central point so as to vaporize an aerosol particle, thereby to induce an avalanche of ionization, commonly known as gas breakdown, as reported by Smith, David C., xe2x80x9cGas Breakdown Initiated by Laser Radiation Interaction with Aerosols and Solid Surfacesxe2x80x9d, J. of Applied Physics, June 1977, p. 2217. The binocular system may comprise a solid lens material such as glass or carbonate, having entry and exit binocular lenses formed at the ends thereof, the solid being laden with aerosol particles.
A problem with that invention is that the ratio of the aperture to the thickness of the lens implies either an extremely thick lens (on the order of several inches thick), or an f number which is difficult or impossible to practically achieve (being on the order of less than 1.2).
2. Disclosure of Invention
Objects of the invention include provision of a simple, low-cost lens for protecting against short pulse laser radiation; a short pulse laser radiation lens being capable of implementation with f numbers higher than f-2; and a practical, effective lens for protecting against short pulse laser radiation.
According to the present invention, a lens array having a plurality of individual lenses combined into a single structure is laden with particulates, such as carbon, or other absorption materials which will readily ionize when radiated by concentrated laser irradiation. According to the invention in one form, a solid plastic or glass lens has a fly""s eye lens surface on both the entry side and the exit side, thereby comprising a plurality of individual lenses, each of which has a very small aperture so that the thickness of the lens array can be just over twice the aperture dimension, thereby providing a compact and practical short pulse laser protection lens assembly.
Other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawing.